Photonic integrated circuit chip packaging

ABSTRACT

A localized hermetic sealing of a photonic integrated circuit component chip mounted in a photonic integrated circuit device chip to protect a chip-to-chip interface from contamination, thereby enhancing functionality and reliability. A covering lid mounted on or over the component chip is hermetically sealed to the device chip surrounding the component chip forming a localized hermetically sealed area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/141,650, filed Apr. 1, 2015, which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to an opto-electronic device, and in particular to an opto-electronic device with a localized hermetically sealed photonic integrated circuit.

BACKGROUND

Opto-electronic chips requiring hermetic sealing may be packaged along with the entire opto-electronic device in a hermetic package, in which the package itself provides hermeticity for the chip. However, hermetic packages are typically more expensive than non-hermetic packages because all optical paths in and out of the hermetic package require a hermetic optical window or a hermetic fiber-feedthrough. Furthermore, all necessary electric connections in and out of the package will also require a hermetic feedthrough.

Telecom transceiver chips may be packaged in a gold box, which provides hermetic sealing of any opto-electronic chips inside. However, since hermetic electrical and optical feedthroughs are more expensive than non-hermetic feedthroughs, the cost for the gold boxes increases rapidly with increasing numbers of electrical pins and optical feedthroughs.

The present invention may provide a solution to eliminate the requirement for a hermetic gold box by providing a localized hermetic sealing around individual components. The localized hermetic seals, may not only eliminate the higher cost attributed to a hermetic gold box, but may also enable the use of less expensive packaging methods that are typically only used in non-hermetic environments.

An object of the present invention is to overcome the shortcomings of the prior art by providing a localized hermetic sealing for photonic integrated circuits.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a photonic integrated circuit (PIC) chip device comprising: a component PIC chip including a component waveguide; a device PIC chip for receiving the component PIC chip, and a device waveguide optically coupled with the component waveguide; a covering lid, for covering the component PIC chip; and a hermetic seal between the covering lid and the device PIC chip forming a localized hermetically sealed area around the component PIC chip.

Another aspect of the present invention relates to a method of assembling a photonic integrated circuit (PIC) device comprising: mounting a component PIC chip onto a PIC device chip; aligning waveguides on the component PIC chip with waveguides on the device PIC chip; fixing the component PIC chip to the device PIC chip; and hermetically sealing a covering lid to an upper surface of the device PIC chip around the component PIC chip, thereby providing a localized hermitically sealed area around the component PIC chip.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein:

FIG. 1 is an isometric view of a first opto-electronic component of a first embodiment.

FIG. 2 is an isometric view of a second opto-electronic component of the first embodiment.

FIG. 3 is a side view of first and second opto-electronic components of a second embodiment.

FIG. 4 is an isometric view of first and second opto-electronic components of a third embodiment.

FIG. 5 is a side view of first and second opto-electronic components of a fourth embodiment with a hermetic covering lid.

FIG. 6 is a side view of first and second opto-electronic components of the fifth embodiment with a hermetic covering lid.

FIG. 7 is a top view of the first and second opto-electronic components.

DETAILED DESCRIPTION

While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art.

With reference to FIGS. 1 and 2, a first exemplary embodiment of the present disclosure includes a first component integrated circuit (IC) chip 1, such as a photonic integrated circuit (PIC), which includes an active or passive opto-electronic component, such as a laser, a semiconductor optical amplifier (SOA) or a photodetector, for integrating into a second device IC chip 2, such as a PIC, which includes one or more passive and active optical, opto-electronic or electronic components. The first component IC chip 1 includes one or more optical component waveguides 3 a and 3 b with a core surrounded by cladding and one or more end facets 4 a and 4 b, respectively, to build a chip-to-chip waveguide interface between the first component IC chip 1 and the second device IC chip 2. The optical component waveguides 3 a and 3 b on the first component IC chip 1 may be surface ridge type waveguides mounted on a substrate 5, as in FIG. 1, or buried waveguides mounted in the substrate 5, as hereinafter described with reference to FIG. 3. The first component IC chip 1 may also include first electrical contacts 6 a and 6 b mounted on the upper surface of the substrate 5 adjacent to the component waveguides 3 a and 3 b for electrically connecting with corresponding second electrical contacts 7 a and 7 b on the second device IC chip 2. The opto-electronic components on the first component IC chip 1 may then be electrically connected to components on the second device IC chip 2, e.g. for power, control or other forms of communication. The first and second IC chips 1 and 2 may be comprised of any material appropriate for IC's and PICs, such as but not limited to Group III-V semiconductors, Silicon, polymers, and glasses. Typically, the first component IC chip 1 is comprised of a different material, e.g. Group III-V, than the second device IC chip 2, e.g. SOI, thereby providing a higher performance component than could be provided in the second IC chip 2.

The first component IC chip 1 may also include a mounting base 8 on which the substrate 5 is mounted or supported, which has an upper surface area greater than that of the substrate 5, whereby a flat ledge or step 9 is formed all the way around the substrate 5. A sealing ring 11 may be provided extending along the ledge 9 surrounding the substrate 5 for hermetically sealing the first component IC chip 1 onto the second device IC chip 2. Accordingly, the ledge 9 forms an integral covering lid for the first component IC chip 1, as hereinafter described.

The base 8 and the ledge 9 may be formed integral with the substrate 5 in a process including forming the sides of the substrate 5 and the waveguides 3 a and 3 b along with the optical facets 4 a and 4 b from the base 8 by removal of portions of a block of material, which includes the substrate 5 and the waveguides 3 a and 3 b, from around the substrate 5. Alternatively, the base 8 may be fabricated in a separate process step and fixed to the substrate 5. The sealing ring 11 on the ledge 9 is lower than the optical component waveguides 3 a and 3 b, so that when the first component IC chip 1 is flipped over during the bonding process, the sealing ring 11 will be above the optical component waveguides 3 a and 3 b.

The second device chip 2, see FIG. 2, includes a substrate 12, which may include at least one cavity or pit 13 extending downwardly from an upper surface 14 thereof and/or at least one surface mounting site. At least one buried optical device waveguide 15, with a core surrounded by cladding, formed in the substrate 12 extends to at least one edge of the pit 13 or surface mounting site. In the illustrated embodiment, the optical device waveguide 15 extends to opposite edges of the pit 13, i.e. includes a break therein, for optically coupling with one or more of the component waveguides 3 a and 3 b forming one or more continuous light paths through the component IC chip 1 when the first component IC chip 1 is mounted in the pit 13. Alternatively, the optical device waveguides 15 may simply extend from one side of the pit 13 to guide light to and/or from the first component IC chip 1.

In a preferred embodiment, the second device IC chip 2 may be comprised of a silicon-on-insulator (SOI) structure formed using CMOS manufacturing procedures, but other structures are also possible. The pit 13 is formed in the second device IC chip 2, e.g. in an etching step, to receive the first component IC chip 1 in a flip chip bonding process described hereinafter. When the first and second IC chips 1 and 2 are bonded together, the optical device waveguide 15 runs underneath the localized hermetic seal ring 11 to guide the light from at least one of the optical waveguides 3 a and 3 b of the first component IC chip 1 from inside the hermetically sealed area to outside thereof.

In the illustrated first embodiment, the second electrical connectors 7 a and 7 b are mounted at the bottom of the pit 13 for mating with the corresponding first electrical connectors 6 a and 6 b, when the first component IC chip 1 is mounted in the pit 13. For the first embodiment, the optical device waveguides 15 extend to the edge of the pit 13 proximate the bottom of the pit 13, whereby mounting of the first component IC chip 1 in the pit 13 aligns both the component waveguides 3 a and 3 b with the optical device waveguides 15, and the first electrical connectors 6 a and 6 b with the second electrical connectors 7 a and 7 b. Accordingly, the depth of the pit 13 corresponds with the combined height of the substrate 5 and component waveguides 3 a and 3 b. Alternative arrangements are also possible, e.g. mounting the second electrical connectors 7 a and 7 b in the sides of the pit 13 and the first electrical connects 6 a and 6 b on the sides of the first component IC chip 1 or mounting the first electrical connectors 6 a and 6 b in or on the ledge 9, inside of the sealing ring 11, and the second electrical connectors 7 a and 7 b on the upper surface of the second device IC chip 2, inside the sealing ring 11. The electrical connectors 6 a and 6 b may be any suitable connectors, including metal leads with an electrically conductive material, e.g. solder, therebetween, wire bonds, and flat pin leads. Electrical leads, vias or traces may extend from the second electrical connectors 7 a and 7 b through a layer of the second device IC chip 2 into contact with electrical and opto-electrical components and devices outside the hermetic area.

A second sealing ring 16 may also be provided on the upper surface 14 of the second device IC chip 2 surrounding the opening of the pit 13 for mating with the first sealing ring 11. Alternatively, only one of the sealing rings 11 or 16 may be provided for hermetically sealing the first component IC chip 1 to the second device IC chip 2 forming a hermetically sealed area only around the first component chip 1, but not the rest of the second device IC chip 2. Typically, the sealing ring 11 and/or 16 may comprise any appropriate material, such as but not limited to metals and metal-alloys. The metallization of the sealing ring 11 may comprise any appropriate metal stack for soldering. The sealing ring 11 may also be formed of alternative bonding materials, such as glass or ceramic, capable of forming a hermetic seal.

The sealing ring 11 and/or 16 may comprise a thermally conductive metal to provide heat dissipation from the first component IC chip 1 to the substrate 12 for reducing or eliminating the requirement for additional cooling of the first component IC chip 1, thereby reducing cost.

The first embodiment is a self-sealing design in which the first component chip 1 and the corresponding second device IC chip 2 have sealing surfaces, e.g. the ledge 9 and the upper surface 14 of the second device IC chip 2 that surround the chip-to-chip optical interface.

With reference to FIG. 3, a second exemplary embodiment of the present disclosure includes a first component IC chip 21, such as a photonic integrated circuit (PIC), which includes an active or passive opto-electronic component, such as a laser, semiconductor optical amplifier (SOA) or photodetector, for integrating into a second device IC chip 22, such as a PIC, which includes one or more passive and active optical, opto-electronic and electronic components. The first component chip 21 includes one or more optical component waveguides 23 with one or more end facets 24, respectively, to build a chip-to-chip waveguide interface between the first component chip 21 and the second device chip 22. In the second embodiment, the optical component waveguides 23 on the first component chip 21 are buried waveguides mounted in the substrate 25. The first component chip 21 may also include first electrical contacts 26 a and 26 b mounted on the upper surface (lower when flipped over) of the substrate or cladding 25, separated from the optical component waveguides 23 by a lower portion of the substrate 25, i.e. cladding, for electrically connecting with corresponding second electrical contacts 27 a and 27 b on the second device chip 22. The opto-electronic components on the first component chip 21 may then be electrically connected to components on the second device chip 22, e.g. for power, control or other forms of communication. The first and second chips 21 and 22 may be comprised of any material appropriate for PICs, such as but not limited to Group III-V semiconductors, Silicon, polymers, and glasses.

The first component chip 21 may also include a mounting base 28 on which the substrate 25 is mounted, which has an upper surface area greater than that of the substrate 25, whereby a flat ledge or step 29 is formed all the way around the substrate 25. A sealing ring 31 may be provided extending along the ledge 29 surrounding the substrate 25 for hermetically sealing the first chip 21 onto the second device chip 22. Accordingly, the ledge 29 forms an integral covering lid for the first component chip 21, as hereinafter described.

The base 28 and the ledge 29 may be formed integral with the substrate 25 in a process including forming the sides of the substrate 25, along with the optical facets 24, from the base 28 by removal of portions of a block of material, including the substrate 5, from around the substrate 5 forming a monolithic PIC structure with the base 28. Alternatively, the base 28 may be fabricated in a separate process step and fixed to the substrate 25. The sealing ring 31 on the ledge 29 is lower than the optical component waveguides 23, so that when the first component chip 21 is flipped over during the bonding process, the sealing ring 31 will be above the optical component waveguides 23.

The second device chip 22, includes a substrate 32, which may include at least one cavity or pit 33 extending downwardly from an upper surface 34 thereof and/or at least one surface mounting site. At least one buried optical device waveguide 35 formed in the substrate 32 extends to at least one edge of the pit 33 or surface mounting site. In the illustrated embodiment, the optical device waveguide 35 extends to opposite edges of the pit 33 or surface mounting site, i.e. includes a break therein, for optically coupling with one or more of the optical component waveguides 23 forming one or more continuous light paths through the component chip 21 when the first component chip 21 is mounted in the pit 33. Alternatively, the optical device waveguides 35 may simply extend from one side of the pit 33 or surface mounting site to guide light to and/or from the first component chip 21.

In a preferred embodiment the second device chip 22 may be comprised of a silicon-on-insulator (SOI) structure formed using CMOS manufacturing procedures, but other structures are also possible. The pit 33 is formed in the second device chip 22, e.g. in an etching step, to receive the first component chip 21 in a flip chip bonding process described hereinafter. When the first and second chips 21 and 22 are bonded together, the optical device waveguide 35 runs underneath the localized hermetic seal ring 31 to guide the light to or from at least one of the optical component waveguides 23 of the first component chip 21 between inside the hermetic area and outside thereof.

In the illustrated first embodiment, the second electrical connectors 27 a and 27 b are mounted at the bottom of the pit 13 for mating with the corresponding first electrical connectors 26 a and 26 b, when the first component chip 21 is mounted in the pit 33. For the second embodiment, the optical device waveguides 15 extend to the edge of the pit 33 proximate the middle of the side of the pit 33, whereby mounting of the first component chip 21 in the pit 33 aligns both the component waveguides 23 with the optical device waveguides 35, and the first electrical connectors 26 a and 26 b with the second electrical connectors 27 a and 27 b. Accordingly, the depth of the pit 33 corresponds with the height of the substrate 25, including cladding and core, alone independent of the raised component waveguides 23, thereby decoupling the height of the component waveguides 23 from the bonding process. Alternative arrangements are also possible, e.g. mounting the second electrical connectors 27 a and 27 b in the sides of the pit 33 and the first electrical connects 26 a and 26 b on the sides of the first component chip 21 or mounting the first electrical connectors 26 a and 26 b in or on the ledge 29, inside of the sealing ring 31, and the second electrical connectors 27 a and 27 b on the upper surface 34 of the second device chip 22, inside the sealing ring 31. The electrical connectors 6 a and 6 b may be any suitable connectors, including metal leads with an electrically conductive material, e.g. solder, therebetween, wire bonds, and flat pin leads. Electrical leads, vias or traces may extend from the second electrical connectors 27 a and 27 b through a layer in the second device IC chip 22 into contact with electrical and opto-electrical components and devices outside the hermetically sealed area.

A second sealing ring 36 may also be provided on the upper surface 34 of the second device chip 22 surrounding the opening of the pit 33 for mating with the first sealing ring 31. Alternatively, only one of the sealing rings 31 or 36 may be provided for hermetically sealing the first component chip 21 to the second device chip 22 providing a hermetically sealed area only around the first component chip 21, but not the rest of the second device chip 22. Typically, the sealing ring 31/36 may comprise any appropriate material, such as but not limited to metals and metal-alloys. The metallization of the sealing ring 11 may comprise any appropriate metal stack for soldering. The sealing ring 11 may also be formed of alternative bonding materials, such as glass or ceramic, capable of forming a hermetic seal.

The sealing ring 31 and/or 36 may comprise a thermally conductive metal to provide heat dissipation from the first component chip 21 to the substrate 32 for reducing or eliminating the requirement for additional cooling of the first component chip 21, thereby reducing cost.

The second embodiment is also a self-sealing design in which the first component chip 21 and the corresponding second device chip 22 have sealing surfaces, e.g. the ledge 29 and the upper surface 34 of the second device chip 22 that surround the chip-to-chip optical interface.

With reference to FIG. 4, a third embodiment includes a second device IC chip 42 substantially identical to the second device IC chip 2 of FIG. 2, with similar reference numerals identifying like elements with similar functions. A first component IC chip 41 includes a similar raised component waveguide 43 with end facets 44, formed on a substrate 45, as in the first component chip 1. The electrical connectors (not shown) are also essentially the same as in the first embodiment.

With reference to FIG. 5, a fourth embodiment includes a second device chip 52 substantially identical to the second device chip 22 of FIG. 3, with similar reference numerals identifying like elements with similar functions. A first component chip 51 includes a similar buried component waveguide 53 with end facets 54, formed on a substrate 55, as in the first component chip 21. First electrical connectors 56 a and 56 b are also essentially the same as in the second embodiment for mating with the second electrical connectors 27 a and 27 b.

However, instead of the ledge 8, the hermetic sealing of the first component chips 41 and 51 are achieved by placing a separate covering lid 62 over the first component chips 41 and 51, and sealing the cover lid 62 to the second device chip 42 and 52. The covering lid 62 may also include a sealing ring 63, similar to the sealing ring 11. The covering lid 62 may be comprised of any appropriate material or combination of materials, such as but not limited to metal, Silicon or glass, to ensure the hermetically sealed area. The covering lid 62 may be a complex structure with mechanical or functional features or may be some form of simple metal, semiconductor wafer or glass part.

When the first component chip 41 or 51 extends upwardly out of the pit 13 or 33 beyond the upper surface 14 or 34 of the second device chip 2 or 22, a cavity 64, which locally receives and covers an upper portion of the first component chip 41 or 51 may be provided in the covering lid 62. A heat spreader 65 comprising a thermally conductive material, e.g. aluminum or copper, may be provided in the cavity 64 in contact with the covering lid 62 and the first component chip 41 or 51 to dissipate heat from the first component chip 41 or 51

Eliminating the need for the ledge 9 and 29 enables the optical facets of the first and second chips 41, 51, 42 and 52 to be fabricated by any appropriate method to form optical waveguide facets, such as but not limited to cleaving, sawing, polishing, and etching. Eliminating the need for the ledge 9 and 29 also decouples the aligning of the first and second chips 41 (51) and 42 (52), respectively, with the aligning and formation of the hermetic seal 11 (31).

FIG. 6 illustrates a fifth embodiment, in which a gap 81 is provided between first and second chips 71 and 72, thereby forming a free space coupling region between the first and second chips 71 and 72. The gap 81 may be provided to reduce coupling losses between the first and second chips 71 and 72, e.g. if the modes sizes of the waveguides 73 and 75 match best with the gap 81. Typically, the spacing between the walls of the first and second PIC chips 71 and 72 may be between 0 μm and 2 μm; accordingly, the gap 81 may be greater than 2 μm, e.g. between 2 μm and 10 μm.

The fifth embodiment also shows an alternative arrangement in which the first component chip 71 may include a recessed optical component waveguide 73, which do not extend to the edge of the first component chip 71 leaving a cladding section 82 between the end of the optical component waveguide 73 and the edge of the first component chip 71 instead of an end facet 74. The fifth embodiment also shows an alternative arrangement in which the second device chip 72 may include a recessed optical device waveguide 75, which does not extend to the edge of the pit 33 leaving a cladding section 84 between the end of the optical device waveguide 75 and the edge of the pit 33. As above, the recessed waveguides may be provided to reduce coupling losses between the first and second chips 71 and 72, e.g. if the modes sizes of the waveguides 73 and 75 match best with the cladding sections 82 and 84. The cladding sections 82 and 84 may be between 0 μm and 20 μm depending on the coupling requirements of the optical component waveguide 73 and the optical device waveguide 75.

The gap 81 may also be filled with a material with a refractive index closely matching that of the waveguides 73 and 75 or the cladding sections 82 and 84, such as epoxy, to reduce back reflections. Alternatively, or in addition, the gap 81 may include at least one lens to further increase the coupling efficiency and reduce coupling losses.

First electrical connectors 26 a and 26 b are provided for mating with corresponding second electrical connectors 27 a and 27 b, as hereinbefore described. Like reference numerals define similar elements with similar functions as the aforementioned embodiments. For the fifth embodiment, the covering lid may be integral with the first component chip 71, i.e. ledge 8 and 29, as in the first and second embodiments, or separate, i.e. covering lid 62, as shown in the third and fourth embodiments.

The optical facets 4 a and 4 b, 24, 44 and 45 and the ledges 9 and 29, on the first component IC chip 1, 21, 41, 51 and 71 may be formed by etching, milling or sawing, as is well known in the art. The optical component waveguides 3 a, 3 b, 23, 43, 53 and 73, and the optical device waveguides 15, 35, 44 and 76 may have any waveguide angle at the optical facet interfaces; however, in a preferred embodiment illustrated in FIG. 7, the device waveguides 15, 35 and 44 form an acute angle a relative to a normal to a sidewall of the pit 13 or 33, and the component waveguides 3 a, 23 and 43 from an acute angle β relative to the normal resulting in a waveguide angle of between 3° and 12° to reduce back reflections. The optical mode sizes at the optical facet interface, between the first and second IC chips 1 and 2 (21 and 22, 41 and 42, 51 and 52, 71 and 72), are not limited in size or shape; accordingly, the IC chips 1 and 2 (21 and 22, 41 and 42, 51 and 52, 71 and 72), may include optical spot size converters.

The second device chip 2, 22, 42, 52 and 72 may hold a plurality of first component chips 1, 21, 41, 51 and 71 in either the same pit 13 or 33 in a plurality of different pits. In particular arrays of SOA's or lasers may be mounted in an array of pits 13 or 33 or in a same pit 13 or 33. The plurality of the first component chips 1, 21, 41, 51 and 71 may be made from different materials or the same materials as each other and as the second device chips 2, 22, 42, 52 and 72.

During the assembly process, see FIG. 3:

Step 1: the first component chip 1 (21, 41, 51, 71) is flipped over and lowered into the pit 13 (or 33) of the second device chip 2 (22, 42, 52, 72) utilizing flip chip bonding alignment devices and procedures.

Step 2: the chip-to-chip waveguide interfaces, e.g. component waveguide 3 a (23, 43, 53, 73) and device waveguide 15 (35, 75) are aligned. For mounting the first component chip 1 (21, 41, 51, 71) to the second device chip 2 (22, 42, 52, 72) precise vertical alignment features may be provided on one of both of the first and second chips. For precise alignment of the first and second chips 1 (21, 41, 51, 71) and 2 (22, 42, 52, 72) both chips may also include corresponding fiducials for use as points of reference during alignment, such as optical imaging alignment. Index matching material, which itself might require hermetic sealing, may be applied between the end facets 4 a, 4 b (24, 44, 54, 74) of the first component chip 1 (21, 41, 51, 71) and the end facets of the device waveguides 15 (35, 75) on the second device chip 2 (22, 42, 52, 72) i.e. in a gap between the first and second chips 1 (21, 41, 51, 71) and 2 (22, 42, 52, 72), respectively, in the pit 13 (or 33). Optical signals may be transmitted through the combined first and second chips to test performance, before final assembly, as is well known in the art.

Step 3: the electrical connectors, e.g. 6 a and 6 b (26 a and 26 b, 56 a and 56 b) to 7 a and 7 b (27 a and 27 b), are connected. In a preferred embodiment, one of the first electrical connector 6 a (26 a, 56 a) or the second electrical connector 7 a (27 a) are provided with a bonding metal, such as solder, which when heated and cooled provides an electrical and a mechanical connection between the first electrical connector 6 a (26 a, 56 a) and the second electrical connector 7 a (27 a), as well as the first component chip 1 (21, 41, 51, 71) and the second device chip 2 (22, 42, 52, 72). Step 3 may be eliminated, if not required, e.g. for a passive optical component. Steps 2 and 3 may be done consecutively in either order or simultaneously. If the electrical connectors are not used to fix the first and second chips together, the first component chip 1 (21, 41, 51, 71) is fixed to the second device chip 2 (22, 42, 52, 72) using any other suitable means.

Step 4: the hermetic seal ring 11 (31, 63) and/or 16 (36) surrounding the first component chip 1 (21, 41, 51, 71) on the upper surface 14 or 34 of the second device chip 2 (22, 42, 52, 72) is closed, thereby providing a localized hermitically sealed area for the component optical waveguides 3 a (23, 43, 53, 73) and the device optical waveguides 15 (35, 75), the facets 4 a and 4 b (24, 44, 54 and 74), and, if required, the electrical connectors 6 a, 6 b, 7 a and 7 b, (26 a, 26 b, 27 a and 27 b). When solder is used for the hermetic seal, the solder is heated until fluid, and then cooled to form a bond between the two surfaces. The assembly process providing the hermetic seal may be done under vacuum or any required inert gas atmosphere, such as but not limited to nitrogen (N₂) or noble gases. In the third, fourth and possibly fifth embodiments step 4 includes mounting the separate covering lid 62 over the first component chip 41, 51 or 71.

Accordingly, the sealing process for the first embodiment may effectively be a one-step self-sealing process, while the second embodiment may be as simple as a two-step process. The device disclosed herein eliminates the need to use an expensive hermetic package for packaging the entire PIC device, including PIC chips, to protect those chips from contamination and exposure to environmental conditions that would reduce lifetime and performance.

The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. 

We claim:
 1. A photonic integrated circuit (PIC) chip device comprising: a component PIC chip including a component waveguide; a device PIC chip for receiving the component PIC chip, and a device waveguide optically coupled with the component waveguide; a covering lid, for covering the component PIC chip; and a hermetic seal between the covering lid and the device PIC chip forming a localized hermetically sealed area around the component PIC chip.
 2. The device according to claim 1, wherein the covering lid is integral with the PIC component chip.
 3. The device according to claim 2, wherein the covering lid comprises a ledge extending from around an end of the component PIC chip.
 4. The device according to claim 3, wherein the device PIC chip includes a pit; and wherein the component PIC chip is mounted in the pit; and wherein the hermetic seal is provided between the covering lid and an upper surface of the device PIC chip.
 5. The device according to claim 1, wherein the covering lid is separate from the PIC component chip.
 6. The device according to claim 5, wherein the covering lid includes a cavity for receiving an upper portion of the component PIC chip.
 7. The device according to claim 5, further comprising a thermally-conductive heat spreader between the device PIC chip and the covering lid for dissipating heat from the device PIC chip.
 8. The device according to claim 1, further comprising a first electrical connector on the component PIC chip, and a second electrical connector on the device PIC chip; wherein the first and second electrical connectors are connected within the localized hermetically sealed area.
 9. The device according to claim 8, wherein the first electrical connector extends from one end of the component PIC chip; and wherein the second electrical connector extends from a bottom of a pit extending into the device PIC chip.
 10. The device according to claim 9, further comprising an electrically conductive bonding material between the first and second electrical connectors bonding the component PIC chip in the pit.
 11. The device according to claim 1, wherein the hermetic seal comprises a thermally conductive metal to dissipate heat from the component PIC chip to the device PIC chip.
 12. A method of assembling a photonic integrated circuit (PIC) device comprising: mounting a component PIC chip onto a PIC device chip; aligning waveguides on the component PIC chip with waveguides on the device PIC chip; fixing the component PIC chip to the device PIC chip; and hermetically sealing a covering lid to an upper surface of the device PIC chip around the component PIC chip, thereby providing a localized hermitically sealed area around the component PIC chip.
 13. The method according to claim 12, wherein the covering lid is integral with the component PIC chip.
 14. The method according to claim 13, wherein the covering lid comprises a ledge extending from around an end of the component PIC chip.
 15. The method according to claim 14, wherein the device PIC chip includes a pit for receiving the component PIC chip; and wherein the hermetically sealing step includes hermetically sealing the covering lid to an upper surface of the device PIC chip.
 16. The method according to claim 13, wherein the component PIC chip includes a substrate in or on which the waveguide is formed; and wherein the method further comprises removing a portion of the substrate to form the ledge.
 17. The method according to claim 12, wherein the hermetically sealing step includes mounting a separate covering lid over the component PIC chip.
 18. The method according to claim 17, wherein the covering lid includes a cavity for receiving an upper portion of the component PIC chip; and wherein a thermally conductive heat spreader is mounted in the cavity for dissipating heat from the component PIC chip.
 19. The method according to claim 12, further comprising connecting electrical connectors on the component PIC chip to electrical connectors on the device PIC chip within the hermetically sealed area.
 20. The method according to claim 12, wherein the hermetically sealing step is conducted under vacuum or any required inert gas atmosphere. 